This invention relates to a method for forming an apertured web, and more particularly to a method for forming an apertured web suitable for use as a topsheet on a disposable absorbent article.
Disposable absorbent articles such as diapers and adult incontinence products are well known in the art. Such disposable absorbent articles collect and retain urine and fecal material deposited thereon by the wearer.
To date, most attempts in the art to handle the urine and fecal material collected and retained in the disposable absorbent article have been directed to handling urine. Dealing with fecal material collected by the disposable absorbent article is simply more difficult than dealing with urine, due to the complex rheology of low-viscosity fecal material.
Exemplary of the urine handling prior art are several attempts to provide disposable absorbent articles having a first topsheet which faces towards and contacts the body of the wearer, and a secondary topsheet under the first topsheet, which either absorbs urine, or transfers the urine to an underlying core for storage until the disposable absorbent article is removed from the wearer.
Typically, the first topsheet and secondary topsheet have different material properties. The secondary topsheet may have a smaller pore size than the first topsheet, to assist in transfer of the urine through the topsheet. The first topsheet may be hydrophobic and more resilient when wetted than the secondary topsheet, in order to pass fluids through the first topsheet to the secondary topsheet.
In yet another attempt in the prior art, the disposable absorbent article has a first topsheet, secondary topsheet and core. The secondary topsheet consists essentially of meltblown hydrophilic fibers and has a pore size greater than the pore size of the core. This arrangement allegedly allows the secondary topsheet to rapidly receive multiple liquid insults and distribute the liquid in the X-Y plane prior to absorption by the core. In yet another attempt, improved vertical wicking capability for urine has been allegedly achieved using inflated cellulose fibers which are free of a surface finish or are crosslinked to one another.
In another attempt in the prior art, an absorbent core suitable for acquiring and containing liquids such as urine in a particularly effective and efficient manner comprises multiple layers. The first layer, which is closest to the wearer, comprises hydrophilic fibrous material and has an acquisition zone of a relatively lower average density than other portions of this layer, in order to quickly acquire discharged liquids. Below the first layer is a liquid handling layer comprising a resilient, low density high void volume material that is moisture insensitive in order to rapidly acquire liquid insults into itself through the acquisition zone and distribute these liquids throughout the liquid handling layer to a storage layer. The storage layer comprises a combination of fibrous material and discrete particles of absorbent gelling material, and allows the liquid handling layer to be drained of the liquids it has acquired, so that the liquid handling layer may have sufficient capacity to acquire and distribute subsequent loadings of liquids.
Examples of such attempts in the prior art include U.S. Pat. No. 4,047,531 issued Sep. 13, 1977 to Karami; U.S. Pat. No. 4,798,603 issued Jan. 17, 1989 to Meyer et al.; U.S. Pat. No. 5,037,409 issued Aug. 6, 1991 to Chen et al.; U.S. Pat. No. 5,124,197 issued Jun. 23, 1992 to Bernardin et al.; and U.S. Pat. No. 5,134,007 issued Jul. 28, 1992 to Reising et al.
Of course, absorbent gelling materials are also now well known in the prior art for their urine handling capability. Absorbent gelling materials are polymeric materials capable of absorbing large quantities of fluids, such as urine, and retaining such absorbed fluids under moderate pressure. The effectiveness of the absorbent gelling materials is quite dependent upon the form, position, and weight percentage of the absorbent gelling materials which are incorporated into the core of the disposable absorbent article.
Recent attempts have been made in the art to provide absorbent gelling materials which have the ability to swell against pressure. These teachings allege to provide the advantage that the absorbent gelling materials absorb fluid under actual pressures exerted by the body during use. Yet other teachings in the art provide absorbent gelling materials having a particular free swell rate and absorbency under load. Alleged advantages of such an absorbent gelling materials are lower volume and mass with approximately the same absorbent capacity, the ability to rapidly absorb a discharged liquid under pressures typically encountered during use, and the ability to retain the absorbed liquid under pressures typically encountered during use.
In another prior attempt, U.S. Pat. No. 4,704,112 issued to Suzuki et al. discloses a facing comprising a nonwoven fabric having two different layers of different fiber compositions. The upper layer has a pattern of apertures therein and is made from hydrophobic fibers and the lower layer has no apertures and is made from hydrophilic fibers.
Examples of such attempts in the prior art include U.S. Pat. No. 5,147,343 issued Sep. 15, 1992 to Kellenberger and U.S. Pat. No. 5,149,335 issued Sep. 22, 1992 to Kellenberger et al.
However, all of these attempts to handle urine do little, if anything, to improve handling of low-viscosity fecal material which may also be present in the disposable absorbent article. Attempts to deal with fecal material include providing a first topsheet which conforms closely to the wearer and has an aperture. The aperture is hopefully registered with the anal opening, so that fecal material passes therethrough into a void space. The first topsheet may comprise various elastic panels in order to closely conform to the skin of the wearer, and/or may have linear elastic strands. Improvements have been made in this area of the prior art, such as optimizing the material properties of the first topsheet. Such optimization makes the first topsheet more comfortable to the wearer and allows a single disposable absorbent article to fit a larger range of sizes of wearers.
Yet other attempts have been made in this area of the prior art to provide an absorbent core with a hole therein, in order to receive the fecal material. The hole may be oblate shaped, so that it is longer and narrower than the aperture in the first topsheet, or may be diamond shaped. The hole in the core may be positioned below an aperture which has elastic strips around its edge.
Improvements to this genre of the prior art disposable absorbent articles also include the addition of spacers. Spacers may be interposed between the first topsheet and the core, in order to ensure a void space is present to receive the fecal material.
Yet other attempts have been made in this genre of the prior art to provide barriers which limit the movement of fecal material to particular portions of the disposable absorbent article. The barriers limit the contact of the fecal material to a lesser portion of the skin of the wearer, than a comparable disposable absorbent article which has no barriers.
Still other attempts in the prior art provide barrier leg cuffs which are upstanding from the plane of the topsheet. The barrier leg cuffs prevent fecal material from breaching the perimeter of the disposable absorbent article.
Examples of such attempts to handle fecal material include U.S. Pat. No. 4,892,536 issued Jan. 9, 1990 to DesMarais et al.; U.S. Pat. No. 4,909,803 issued Mar. 20, 1990 to Aziz et al.; U.S. Pat. No. 4,968,312 issued Nov. 6, 1990 to Khan; commonly assigned U.S. Pat. No. 4,990,147 issued Feb. 5, 1991 to Freeland; commonly assigned U.S. Pat. No. 5,037,416 issued Aug. 6, 1991 to Allen et al.; U.S. Pat. No. 5,062,840 issued Nov. 5, 1991 to Holt et al.; commonly assigned U.S. Pat. No. 5,171,236 issued Dec. 15, 1992 to Dreier et al.; and European Patent Application 0,355,740 A2 published Feb. 28, 1990 to Enloe.
However, none of these attempts to handle fecal material solve the problem of low-viscosity fecal material which is predominately prevalent in younger children, particularly those who are breast fed. Low-viscosity fecal material easily migrates within the disposable absorbent article under the influences of gravity and motion or pressure by the wearer.
The migration of the fecal material often moves it towards the perimeter of the disposable absorbent article, increasing the likelihood of leakage. The migration of the fecal material also smears it against the skin of the wearer, making cleanup more difficult. In order to clean the wearer, the caretaker must wipe the entire area of the skin which has encountered the fecal material and typically has to deal with a relatively large soiled area.
One attempt in the art to handle low-viscosity fecal material is found in U.S. Pat. application Ser. No. 08/076,713 filed Jun. 11, 1993 in the name of Roe. This application is a disposable absorbent article having a first topsheet with a high trans-topsheet penetration overlaying a secondary topsheet having a lesser trans-topsheet penetration.
The invention is a method for forming an apertured web which may be used as a topsheet on a disposable absorbent article, such as a diaper. The web is fed in a machine direction through a first nip formed by a pair of rollers one of the rollers having a smooth outer surface and the other roller having an outer surface with a plurality of projections extending from it""s outer surface. At least one of the rollers forming the first nip is heated, preferably both rollers are heated. As the web passes through the first nip a plurality of apertures are created each having a fused perimeter. The web is cooled to solidify the fused perimeter of the apertures. The web is then fed through a second nip formed by a pair of rollers to break the solidified fused perimeter of the apertures. One of the rollers of the second nip has an outer surface comprising a plurality of grooves.
The web may be fed through a third nip formed by a pair of rollers to further break the fused perimeter of the apertures. One of the rollers of the third nip has an outer surface comprising a plurality of grooves.